Organic electroluminescent element and method for manufacturing the same

ABSTRACT

An organic electroluminescent element which is highly precise and minute, uniform in light emission, free from cross talk, resistant to external pressure, and further excellent in sealing properties and a process for producing the above element. The organic electroluminescent element  1  which is equipped, between a lower electrode  3  and a counter eletrode  4  each on a substrate  2,  with an intervening organic layer  5  comprising a light-emitting layer, comprises an inter-insulator film  6  having a coefficient of water absorption of at most 0.1% in a non-light-emitting element portion; step portions  9  in the inter-insulator layer  6  which define the boundary between a light-emitting element portion and a non-light-emitting element portion and which comprise rising parts almost perpendicular to the surface of the lower electrode  3;  and a sealing plate or a sealing lid  7  which is placed over the inter-insulator layer  6  and which is attached to the substrate  2  via an adhesive layer  8.

TECHNICAL FIELD

The present invention relates to an organic electroluminescent element.More particularly, the present invention is concerned with an organicelectroluminescent element (hereinafter sometimes abbreviated to“organic EL element”) which, when used for a display and the like, ishighly precise and minute, uniformly emits light, and can withstandexternal pressure.

BACKGROUND ART

Organic electroluminescent elements have heretofore been developed foruse as a display. The organic electroluminescent element to be used as adisplay is required to have high precision and minuteness in patterning,uniformity in a light-emitting surface and precision in the edge of alight-emitting surface. The organic electroluminescent element is alsorequired to solve such problems by a minute short-circuit occurring atan edge of an electrode, thereby causing cross talk in a display. Thereis known an element in which a sealing plate is clad to a substrate forthe purpose of sealing an organic EL element. The sealing plate has thetendency to be thinner, as a display is required to be thinner, that is,minimized in thickness.

However, a thin sealing plate results in a problem that the sealingplate is brought into contact with an element by impact or externalpressure with the result that the plate is destroyed.

Japanese Patent Application Laid-Open No.250583/1991 ( Hei-3) disclosesan organic EL element which is equipped with an interlaminar insulatingfilm, and thus has favorable pattern precision as well as highuniformity in a light-emitting surface. However, since a masking vapordeposition method is applied to the production of a counter electrode,it has been still difficult to produce a highly precise and minutedisplay having a line pitch of 300 μm or less.

In addition, Japanese Patent Application Laid-Open No.101884/1993(Hei-5) discloses an organic EL element which is equipped with aninter-insulator layer, and the outside surface of which is covered witha moisture-resistant film. Nevertheless the organic EL element thusdisclosed has still a problem that because of the insufficient sealingpower of the moisture-resistant film, a cathode is attacked by moistureor oxygen after being allowed to stand for several thousands hours, thusbringing about a dark spot, that is, defective light emission.

Moreover, Japanese Patent Application Laid-Open No. 275172/1993(Hei-5)discloses a highly precise and minute display having a line pitch ofabout 100 μm , by equipping an organic EL element with aninter-insulator layer in the form of a wall, and also forming a cathodeby means of oblique vapor deposition. However, the display disclosedabove has still the problem that a minute short circuit is caused byreason of the deviation of the alloy composition in the edges (the endaway from the inter-insulator layer) of the electrode that is formedthrough vapor deposition in an oblique direction to the substrate.

DISCLOSURE OF THE INVENTION

An object of the present invention is to overcome the above-mentioneddisadvantages inherent to the conventional techniques, and at the sametime, to provide an organic electroluminescent element which is highlyprecise and minute, capable of uniformly emitting light, free from crosstalk, capable of withstanding external pressure, and also excellent insealing properties.

It has been found that an organic electroluminescent element which isequipped with a vertically rising inter-insulator layer and with asealing plate above the aforesaid film, is a highly precise and minutedisplay which is free from cross talk, low in production cost, and canbe miniaturized and made thinner.

The first aspect of the present invention provides an organicelectroluminescent element 1 that is equipped, between a lower electrode3 and a counter eletrode 4 each on a substrate 2, with an interveningorganic layer 5 comprising a light-emitting layer, which element 1comprises an inter-insulator layer 6 having a coefficient of waterabsorption of at most 0.1% in a non-light-emitting element portion; stepportions 9 in said inter-insulator layer 6 which define the boundarybetween a light-emitting element portion and a non-light-emittingelement portion and which contain rising parts almost perpendicular tothe surface of said lower electrode 3; and a sealing plate or a sealinglid 7 which is placed over said inter-insulator layer 6 and which isattached to said substrate 2 via an adhesive layer 8. (Refer to FIG. 1.)

The second aspect of the present invention provides a process forproducing an organic electroluminescent element 1, comprising at leastone step of forming a lower electrode 3 on a substrate 2; a step offorming a patterned inter-insulator layer 6 on said lower electrode 3; astep of forming an organic layer 5 on said lower electrode 3; and atleast one step of forming a counter electrode 4 in the form of film, sothat step portions 9 in said inter-insulator layer 6 define the boundarybetween a light-emitting element portion and a non-light-emittingelement portion and also contain rising parts almost perpendicular tothe surface of said lower electrode 3, said counter electrode 4 is cutoff by said step portions 9 at the rising parts so as to be subjected topatterning processing, and said counter electrode 4 is in close contactwith said inter-insulator layer 6 at said step portions 9 adjacent tosaid substrate 2.

The third aspect of the present invention provides an organicelectroluminescent element 1 that is equipped, between a lower electrode3 and a counter eletrode 4 each on a substrate 2, with an interveningorganic layer 5 comprising a light-emitting layer, which element 1comprises an inter-insulator layer 6 having a coefficient of waterabsorption of at most 0.1% in a non-light-emitting element portion; stepportions 9 in said inter-insulator layer 6 which contain portions risingin the form of an inverse taper almost perpendicularly to the surface ofthe lower electrode 3 and divide said counter electrode 4 into aplurality of individuals; and a sealing plate or a sealing lid 7 whichis placed over said inter-insulator layer 6 and which is attached tosaid substrate 2 via an adhesive layer 8.

The fourth aspect of the present invention provides an organicelectroluminescent element 1 that is equipped, between a lower electrode3 and a counter eletrode 4 each on a substrate 2, with an interveningorganic layer 5 comprising a light-emitting layer, which element 1comprises a first inter-insulator layer having a trapezoidal crosssection 15 on said lower elecrode 3 as a non-light-emitting elementportion; a second inter-insulator layer 14 above said trapezoidal crosssection (on the opposite side of said lower electrode 3) ; step portions9 in said second inter-insulator layer 14 which contain rising partsalmost perpendicular to the surface of the lower electrode 3 and dividesaid counter electrode 4 into a plurality of individuals; and a sealingplate or a sealing lid 7 which is placed over said secondinter-insulator layer 14 and which is attached to said substrate 2 viaan adhesive layer 8. (Refer to FIG. 2.

The fifth aspect of the present invention provides a process forproducing an organic electroluminescent element 1, comprising at leastone step of forming a lower electrode 3 on a substrate 2; a step offorming a patterned inter-insulator layer on said lower electrode 3; astep of forming an organic layer over said lower electrode 3; and atleast one step of forming a counter electrode 4 in the form of film sothat a first inter-insulator layer 15 has a trapezoidal cross section, asecond inter-insulator layer 14 is mounted above said trapezoidal cross( section on the opposite side of said lower electrode 3 ), stepportions 9 in said second inter-insulator layer 14 contain rising partsalmost perpendicular to the surface of said lower electrode 3, and saidcounter electrode 4 is subjected to patterning processing at said risingportions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. is a cross-sectional view showing an organic EL elementaccording to the first aspect of the present invention;

FIG. 2 is a cross-sectional view showing an organic EL element accordingto the fourth aspect of the present invention;

FIG. 3 is a cross-sectional view showing an inter-insulator layer on asubstrate;

FIG. 4 is a cross-sectional view showing a counter electrode at the timeof vapor deposition in an oblique direction to the substrate;

FIG. 5 is a cross-sectional view showing a counter electrode after vapordeposition in the present invention;

FIG. 6 is a cross-sectional view showing an inter-insulator layer etc.according to the third aspect of the present invention;

FIG. 7 is a cross-sectional view showing an inter-insulator layer at thetime of its film forming;

FIG. 8 is a cross-sectional view showing a photoresist after patterning;

FIG. 9 is a cross-sectional view showing etching process in a patterningstep;

FIG. 10 is a view showing a cross-sectional configuration of aninter-insulator layer;

FIG. 11 is a stereograph at the time of forming two layers ofinter-insulator layer;

FIG. 12 is a view when an X-Y matrix is observed from upside;

FIG. 13 is a cross-sectional view showing an X-Y matrix;

FIG. 14 is a circuit diagram at the time of driving an active matrix;and

FIG. 15 is a plan view showing an example at the time of driving anactive matrix.

The symbols in the above-mentioned drawings shall have the followingdesignation.

1. organic EL element

2. substrate

3. lower electrode

4. counter electrode

5. organic layer

6. inter-insulator layer

7. sealing plate

8. adhesive layer

9. step portion

10. edge of counter electrode

11. photoresist subjected to patterning processing

12. etching portion

13. opening portion

14. second inter-insulator layer

15. first inter-insulator layer

20. SCAN electrode wire

21. DATA electrode wire

22. COMMON electrode wire

23. capacitator

24. pixel electrode

25. opening for inter-insulator layer

THE MOST PREFERRED EMBODIMENTS TO CARRY OUT THE INVENTION

In the following, the present invention will be described in moredetail.

First of all, some description will be given of the inter-insulatorlayer which constitutes the organic electroluminescent element accordingto the present invention.

An organic electroluminescent element is known in which an organic layerallowing current to flow is made to intervene between a pair of a lowerelectrode and a counter electrode. A portion in which an insulator layeris made to intervene between a lower electrode and a counter electrodeprevents current from flowing, and accordingly can not emit light. Thussaid portion constitutes a non-light-emitting portion. Such an insulatorlayer is designated as inter-insulator layer. A technique is known,which carries out pattern processing of a light emitting element by thepattern processing of an inter-insulator layer [note to Japanese PatentApplication Laid-Open No.250583/1991(Hei-3)].

It is indispensable in the present invention that step portions of aninter-insulator layer rise almost perpendicularly, said step portionsbeing positioned at a boundary separating a non-light-emitting elementportion equipped with an inter-insulator layer from a non-light-emittingelement portion not equipped with an inter-insulator layer. By using “h”for the height of an inter-insulator layer, “W₁” for the width of thetop part of the inter-insulator layer, and “W₂” for the width of thebottom part of the inter-insulator layer, the configuration of theinter-insulator layer in FIG. 3 is expressed by the following formula:$a \approx \frac{W_{2} - W_{1}}{2}$

In the present invention, a<(h/7) is preferable, and a<(h/10) isparticularly preferable. It is made to a<0 when the step portions areprocessed to form an inversely tapered shape, which is one of the mostpreferable configurations in the present invention. The height of aninter-insulator layer (h) is preferably in the range of 0.5 mμ to 50 mμ.The height of an inter-insulator layer (h), when being in theaforestated range, enables a counter electrode 4 to be cut off at thestep portions of the inter-insulator layer and at the same time, to besubjected to patterning processing.

There has heretofore been known a technique of pattern processing acounter electrode by applying vapor deposition in an oblique directionto form the counter electrode [Japanese Patent Laid-Open No.275172/1993(Hei-5), in particular], since it has been impossible to formsuch a rising step portion. The foregoing vapor deposition technique,which applies vapor deposition in an oblique direction to theinter-insulator layer in order to form the counter electrode, hasinvolved the problems that an edge of the counter electrode 4 is formedas shown in FIG. 4 and thus a short circuit and nonuniformity of lightemission are liable to take place at the edge portion 10. In addition,the foregoing technique has involved the problem that the processablityof a minute pattern is lessened by the decrease in the pattern precisiondue to the deposition passing around at the time of vapor deposition.

As opposed to the aforestated conventional technique, since the stepportions 9 of the inter-insulator layer rise almost perpendicular, it ismade possible thereby to spontaneously cut off the counter electrode atthe step portion 9, and thus to pattern process the counter electrode bydispensing with a special method such as the oblique vapor deposition.In the first and the second aspects of the present invention, thecounter electrode 4 of the light-emitting element portion is in contactwith the cross section of the adjacent inter-insulator layer 6 at thepattern processed portion. The first and second aspects of the presentinvention are each characterized by the absence of a counter electrode 4which is apart from said cross section, whereby the advantages of thepresent invention are derived (FIG. 5). In the following, the workingeffects due to the above advantages will be described.

(a) The pattern precision is surprisingly excellent enabling evenseveral μm of precision, since the pattern of the counter electrode 4 isdetermined by the pattern of the interlaminar insulating film 6 as such.

(b) The light emission is freed from non-uniformity, since the counterelectrode 4 is freed from compositional non-uniformity or productivenon-uniformity at the edge of the counter electrode 4. It has been madepossible to prevent non-uniformity from occurring in the electric field,and also to prevent short circuit as well as cross talk. In addition, itis advantageous that the edge of the light-emitting element portion ofthe counter electrode 4 is less prone to be oxidized, since it is incontact with the inter-insulator layer.

(c) Since the patterning of the inter-insulator layer 6 itself ispossible even with a precision of 1 μm by the use of photolithographymethod, the patterning precision of the counter electrode 4 is enhanced,and the highly precise minute patterning of the counter electrode 4 isalso made possible. The patterning is favorably applicable to the userequiring a high resolution display, a printer head and the like inorder to realize several μm of the pitch.

Likewise in the third aspect of the present invention, it is possible tocut off the counter electrode 4 at the step portion 9 and to processpatterning of the same. In the case of inversely tapered shape, even forthe presence of bending around of vapor deposition, the deposits areprevented from adhering to the step portion, thereby enabling morereliable cutting off. The advantages in the third aspect of the presentinvention are same as the description in the items (a) and (b), therebyenabling high resolution and high density patterning of the cathode.However in the third aspect of the present invention, as shown in FIG.6, the counter electrode 4 must not entirely cover the organic layer 5,or cause short circuits to the lower electrode 3.

In the fourth and fifth aspects of the present invention, as shown inFIG. 2, the light-emitting pattern is established by installing thefirst inter-insulator layer 15, and at the same time, the counterelectrode 4 is pattern processed with the second inter-insulator layer14 rising almost perpendicular. The reason for using the firstinter-insulator layer 15 is directed to the prevention of electriccurrent flow even in the case of poor adhesion between the secondinter-insulator layer 14 and the edge of the counter electrode, bydefinitely eliminating a malfunctioning portion such as short circuitsoccurring at the edge.

By virtue of the aforesaid constitution, the foregoing effects (a), (b),and (c) are assured. Moreover, the second inter-insulator layer 14 maybe inversely tapered, or may be such that satisfying the inequalitya<(h/10).

The materials of construction for the inter-insulator layer to be usedin the present invention need to be the materials which enable highlyprecise and minute patterning. Preferably usable specific examplesthereof include a variety of insulating polymers, insulating oxides,insulating nitrides and insulating sulfides. Examples of particularlypreferable polymers include fluorinated polyimides, polyolefin,fluorine-based polymers and polyquinoline. Examples of particularlypreferable oxides include SiO_(x)(1<x<2), SiO₂, fluorine-added SiO₂ andAl₂O₃. Examples of preferable nitrides include SiN_(y)(1<y<4/3), SiONand AlSiON. Examples of preferable sulfides include ZnS.

An inter-insulator layer of low hygroscopicity is preferably used inaddition to that of insulating property. Particularly preferableinter-insulator layer 6 is are having a water absorption (coefficient ofwater absorption) of at most 0.1% . An inter-insulator layer of highhygroscopicity causes, in the case of preserving the elements, oozingout of water which has mixed in during the preparation, thereby oxidizesthe electrode of the element, deteriorates the element and furtherbecomes responsible for defects in light emitting elements (dark spot).The use of a polymer of low hygroscopicity is preferable because of, inparticular its excellent processability. Particularly preferableinter-insulator layer is that of fluorine base or polyolefin base. Thehygroscopicity is evaluated as coefficient of water absorption accordingto ASTM D-570.

The inter-insulator layer is not necessarily required to have aphotosensitive function, but preferably has such a function in somecases, since said function enables photolithography without the use of aphotoresist. A photosensitive material is available in the marketwhether it is an inorganic oxide or a polymer.

In the following, detailed description will be given of the filmpreparation process for the inter-insulator layer as well as thepatterning process. From among a variety of film preparation processesand patterning processes that are available in the present invention,typical examples by the use of photolithography will be describedhereunder.

(i) Film Preparation for the Inter-insulator Layer.

In the case of an insulative polymer, a solution of a polymer or aprecursor thereof is made into a film by means of coating, spin coating,dipping or the like process (refer to FIG. 7) In the case of aninsulative inorganic oxide, a variety of film preparation processes areavailable including vapor deposition, CVD, plasma CVD, ECR-CVD,sputtering, ECR-sputtering and the like processes.

(ii) Photosensitization and Development of Photoresist.

The patterning of a photoresist is carried out by photosensitizing anyof various available photoresists, and developing the same (refer toFIG. 8). A photoresist and an exposure method are each selected inaccordance with the minuteness and precision of the pattern that arerequired in each case. Various exposure methods are known andexemplified by contact exposure method and cutback exposure method.

(iii) Patterning Step.

A portion uncovered with a photoresist is removed by any of variousetching methods (refer to FIG. 9). Examples of the etching methodsinclude wet etching method in which an inter-insulator layer isdissolved and removed with a solvent and dry etching method in which aninter-insulator layer is decomposed and removed with a plasma or thelike. In order to allow an inter-insulator to rise almost perpendicularto the surface of the lower electrode 3, the dry etching method ispreferable.

In the case of using the wet etching method, it is necessary to employ asolvent having a high etching rate for the inter-insulator layer in thedirection perpendicular to the substrate. In the case where such asolvent is available for any of a variety of inter-insulator layers, theuse of the wet etching method is preferable from the viewpoint ofreducing the production cost and enhancing the productivity.

In the case of using the dry etching method, it is important to select asuitable etching gas. Dry etching by the use of oxygen plasma ispreferable for such a polymer as fluorinated polyimides, polyolefins andpolyquinolines. On the other hand for fluorine-based polymers,fluorine-added SiO₂, SiO₂ and Al₂O₃, it is preferable to employ, as aetching gas, a fluorinated carbonized gas which has been made into aradical form with a plasma. Examples of particularly preferablefluorinated carbonized gas include CHF₃ and CF₄. It is also preferableto employ a halogenated boron gas or a fluorinated carbonized gas thatis mixed with oxygen, argon or the like.

By the above-mentioned procedures, the preparation steps of theinter-insulator layer can be completed. There is available, however,another film preparation process, for example, a process in which anoxide-mixed paste is made into a film and patterned by means of a screenprinting method or the like, and thereafter the resultant patterned filmis fired at several hundreds centigrade to prepare an inter-insulatorlayer.

In the following, some description will be given of the counterelectrode and the process for producing the same as well as a sealingplate.

A counter electrode 4, when being used as a cathode, is preferably madeof an alloy containing an alkali metal or an alloy containing analkaline earth metal. Examples of particularly preferable alloys amongthem include Mg:Ag, Al:Li, Pb:Li, Zn:Li, Bi:Li, Ln:Li, Al:Ca, etc. It isknown that the above-exemplified alloys are relativelycorrosion-resistant and have each a low work function.

In the preparation of films by using said alloy, a vapor depositionmethod and a sputtering method, especially the sputtering method arepreferably used. There is no need at all in the present invention, forcarrying out oblique vapor deposition. On the contrary in order toassure the organic EL element according to the present invention, thevapor deposition should be carried out perpendicularly to the surface ofa substrate.

A counter electrode 4, when being used as an anode, is preferably madeof a transparent oxide. Examples of particularly preferable oxideinclude ITO, ZnO:Al, SnO₂: Sb and InZnO(indium/zinc oxide).

In the organic EL element according to the present invention, a sealingplate is positioned over the inter-insulator layer 6 or the secondinter-insulator layer 14. Preferable materials of construction for thesealing plate or sealing lid are glass, an oxide and a nitride ceramiceach in the form of a thin plate. Preferable thickness of the sealingplate or sealing lid is 5 μm to 2 mm, and it is at most 500 μm in orderto obtain particularly thin organic EL element.

It has heretofore been a problem that when a thin sealing plate is used,it is brought into contact with the body portion of the organic ELelement by the external pressure or impact, thus leading to the breakageof the organic EL element. With regard to the present invention,however, the inter-insulator layer 6 or the second inter-insulator layer14 functions as a column, and prevents the sealing plate from cominginto contact with the body of the organic EL element. It is therefore,made possible to make thinner the whole organic EL element by thinningthe sealing plate 7, without causing any problem even if the sealingplate 7 is made as thin as 50 μm.

In the following, detailed description will be given of the preferredembodiments of the present invention.

First of all, the preferred embodiments of the sealing plate are asfollows.

(a) The space encompassed by the sealing plate 7 and the substrate 2 isfilled in with a fluorinated hydrocarbon as a sealing liquid to promotethe heat radiation properties and at the same time, enhance the sealingcharacteristics.

(b) The space encompassed by the sealing plate 7 and the substrate 2 isincorporated with a moisture absorbing agent preferably exemplified byzeolite, silica, calcined gypsum and calcium carbonate.

(c) A moisture absorbing layer is placed on the inner side (instead ofthe outer side which is in contact with the outside of the organic ELelement) of the sealing plate 7. Examples of the moisture absorbinglayer include not only a layer of a moisture absorbing polymer, a layerof the mixture of a moisture absorbing polymer and a moisture absorbingagent, but also a layer in which a moisture absorbing agent is fixed onthe inner side of the sealing plate by means of a resin which has beencured by ultraviolet ray or heat. Examples of the moisture absorbingpolymer include polyamide, polyvinyl alcohol and polyvinyl butyral.

(d) The space encompassed by the sealing plate 7 and the substrate 2 ispreferably incorporated with a sealing gas such as dehydrated nitrogen,carbon dioxide or helium.

(e) It is possible to enhance the color purity of light emission orcontrast by placing a color filter on the sealing plate at the time ofwithdrawing light from the counter electrode.

(f) Likewise, it is possible to enhance the color purity of lightemission or contrast by placing a color filter in the sealing plate andabove the counter electrode at the time of withdrawing light from thecounter electrode.

(g) Further it is possible to convert the color of emitted light byplacing a color conversion film in the sealing plate and above thecounter electrode. A color can be converted from blue to red or orange,from green to red or orange, from blue to green or white and so forth.The color conversion film has been subjected to patterning, and thereare separately available in parallel, films which convert to green, andred, respectivly.

The cross sectional configurations of the inter-insulator layer 6 andthe second inter-insulator layer 14 in the present invention includethree embodiments (a), (b), (c) and the like as shown almost against thesubstrate surface in FIG. 10. It is preferable in the present inventionthat the relationship |a|<(h/7) is satisfied. The embodiment (b) or (c)corresponds to the case of a<0, and is characterized in that the crosssection is processed in the inversely tapered shape, thus renderingitself one of the preferable embodiments. The reason is that the counterelectrode 4 under the above-mentioned embodiment is cut off without failat step portions.

There exist step portions of the inter-insulator layer in the presentinvention, but it is possible to form portions where the counterelectrode 4 is not cut off. As an example, when a taper of a>(h/5) isprocessed at the step portion 9, there is no need for cutting thecounter electrode.

As illustrated in FIG. 11, a portion that is encompassed by a risingcross-section and a taper cross-section, can be formed at the opening ofthe inter-insulator layer which constitute the light emitting elementportion by a method wherein two layers of the inter-insulator layers areformed, specifically, by allowing a first step portion of the film torise perpendicularly and subjecting a second step portion of the film totaper processing. The counter electrode is cut off at the risingportion, but is not cut off at the taper cross-section.

The fourth and the fifth aspects of the present invention take advantageof the foregoing facts. That is to say, at the first inter-insulatorlayer 15, the cross section is formed into a trapezoidal shape so thatthe counter electrode may not be cut off and so that the film is usedfor establishing the light-emitting pixel surface. On the contrary, atthe second inter-insulator layer 14, the step portions are made to risealmost perpendicularly so that the counter electrode may be cut off andso as to enable patterning by taking advantage of the layer.

It is also possible in the present invention to apply vapor depositionmasking so that a counter electrode 4 may not be formed on theinter-insulator layer [note Japanese Patent Application Laid-OpenNo.250583/1991(Hei-3)]. Accordingly, a portion free from a counterelectrode 4 can be formed on the inter-insulator layer.

The above-mentioned present invention is preferably usable as theembodiments as described hereunder.

(i) It is possible in the present invention to form a large number oflower electrodes 3 in the form of parallel stripe type electrodes, andfurther to form a large number of inter-insulator layer of the presentinvention in the form of stripes that are perpendicular to the aforesaidstripes. By applying the invention to this embodiment, an X-Y typematrix can be formed.

FIG. 12 is a view when such an X-Y type matrix is observed from upside,and FIG. 13 is a cross sectional view of this X-Y type matrix.

(ii) It is not necessary to form the X-Y type matrix as described in thepreceding item (i) in the case of TFT driving or active matrix driving,but in any case like this it is made possible to use the organic ELelement according to the present invention.

As an example, the circuit as illustrated in FIG. 14 is incorporated pereach pixel in active matrix driving using a transistor. In theconstitution of the circuit arrangement in FIG. 15, if opening portionsof the inter-insulator layer according to the present invention areprovided only at the end portion 25 and the portion corresponding to thepixel electrode, it follows that the counter electrodes Tr₁ and Tr₂, thecounter electrodes on SCAN( 20 ), DATA( 21 ), and COMMON( 22 ) and thecounter electrode on the pixel electrode are insulated by the stepportions of the inter-insulator layer.

It is therefore, made possible to avoid the electrical communication ofTr₁, Tr₂, SCAN, DATA, and COMMON with the counter electrode 4 on thepixel electrode, by passing electric current only through the counterelectrode 4 on the pixel electrode. Pixel defects have heretofore beenfrequently caused by the electrical communication of Tr₁, Tr₂, SCAN,DATA, and COMMON with the counter electrode owing to the defect of theinter-insulator layer. However such a malfunctioning can be avoided bysaid constitution.

Moreover, an additional inter-insulator layer is installed in advance onthe portion at which the SCAN, DATA, and COMMON intersect the counterelectrode 4, on the portion at which the COMMON intersects the SCAN, andalso on the portion at which the SCAN intersects the DATA so as toinsulate one another. The above-mentioned additional inter-insulatorlayer, different from the inter-insulator layer according to the presentinvention, are not equipped with perpendicular step portions so that theelectrode wires above the additional inter-insulator layer may not becut off. Accordingly, it is acceptable in the present invention topartially use an inter-insulator layer having non-perpendicular stepportions.

In the following, the present invention will be described in more detailwith reference to working examples, which however, shall not limit thepresent invention thereto.

EXAMPLE 1 Preparation of Inter-Insulator Layer

ZCOAT-1410 (photosensitive polyolefin-based nagative type resist,produced by Nippon Zeon Co.,Ltd.) was used to form a film by spincoating on a glass substrate 2 having a thickness of 0.5 mm and holdingan ITO as a lower electrode which had been subjected to stripedprocessing at a pitch of 300 μm. The spin coating was carried out at anumber of revolutions of 1500 rpm for a revolution time of 35 seconds.The film obtained in the aforesaid manner had a thickness of 5.3 μm.Subsequently, the film-coated substrate was baked in a hot oven at 70°C. for 30 mimutes, and then was exposed to light through a photomask atan irradiation power of 120 mJ/cm² with ultraviolet ray at a wavelengthof 436 nm. The exposure pattern was carried out so that the ZCOAT-1410as the inter-insulator layer having a width of 20 μm remained at every100 μm as linear lines perpendicularly to the pattern of the aforesasidITO pattern. After development, curing was put into practice at 250° C.for 2 hours in a clean oven to prepare an inter-insulator layer.

EXAMPLE 2 Evaluations for Perpendicularity of Inter-Insulator Layer andMoisture Absorption Property

The specimen that had been prepared in the preceding Example 1 wasbroken at an arbitrary point thereof into ten specimens sized 2 mm×2 mm,the cross sections of which were observed by the use of a scanningelectron microscopy. Thus, measurements were performed to obtain thevalue: {(width of the lower section)−(width of the uppersection)}/(height) at 20 places of the specimens. As a result, the valuewas {fraction (1/10)} or less for all of the specimens. At the sametime, measurements were performed to obtain the coefficient of waterabsorption (moisture absorption) of the specimen which had been preparedin Example 1. As a result, the the moisture absorption showed favorablevalues of 0.07% (in accordance with ASTM D 570).

EXAMPLE 3 Preparation of Organic EL Element and Evaluation of Precisionand Minuteness Thereof

The specimen which had been prepared in Example 1 was cleaned withultrasonic wave in isopropyl alcohol for 3 minutes, and further with acleaning apparatus using the combination of ultraviolet ray and ozonefor 30 minutes. Subsequently, the specimen was placed in a vacuumdeposition apparatus available from the market (produced by ULVAC JAPANLtd.), and was fixed to a substrate holder. Then 200 mg of N,N′-diphenyl-N, N′-bis-(3-methylphenyl)-[1, 1′-biphenyl]-4, 4′-diamine(hereinafter abbreviated to “TPD”) was placed in a resistance heatingboat made of molybdenum, and in another resistance heating boat made ofmolybdenum was placed 200 mg of tris (8-hydroxyquinolinol)aluminum(hereinafter abbreviated to “Alq”). Subsequently, a vacuum chambercontainig the boats was evacuated to 1×10⁻⁴ Pa.

Thereafter, the TPD-containig boat was heated to form a holetransporting layer having a film thickness of 80 nm. Without taking outthe boat out of the vacuum chamber, there was prepared a light-emittinglayer in the form of film consisting of Alq and having a film thicknessof 75 nm on the hole transporting layer. Subsequently, without openingthe vacuum chamber, Mg and a tungsten basket containing silver that wereplaced in a resistance heating boat and prepared in advance in a vaccumchamber, were heated to prepare a film of Mg-Ag counter electrode havinga film thickness of 200 nm at vapor deposition rates of Mg and Ag of 1.4nm/sec. and 0.1 nm/sec., respectivly. By the above-described proceduresan organic EL element prior to sealing was completed.

Thereafter, a sealing plate was adhesively bonded onto the resultantorganic EL element in an inert gas (N₂). The sealing plate used hereinwas a glass plate with a thickness of 100 μm which had been subjected todehydration treatment by the use of a dehydrating agent which had beenprepared by dispersing silica-gel in a solution of soluble nylon. Bydefining the surface to which the dehydrating agent attached as theelement side, the periphery of the sealing plate was coated with aultraviolet ray curing adhesive, and the sealing plate and the organicEL element were attached to each other to seal them by ultraviolet rayirradiation. As the result, a sealed organic EL element according to thepresent invention was completed. The resultant sealed organic EL elementhad a thickness as small as 0.6 mm, thus demonstrating theefffectiveness of the organic EL element according to the presentinvention as described hereinbefore.

Subsequently by selecting one line of ITO and one line of Mg:Ag out ofthe stripe lines, a voltage of 7 V was applied using ITO as the anodeand Mg:Ag as the cathode to examine the precision of the pattern by theuse of an optical microscope. As a result, the precision of the patternwas remarkably favorable, showing ±1 μm , and only the intersecting partof the stripes of the ITO and the Mg:Ag emitted light.

In addition, voltage was applied to all stripe lines of the Mg:Ag toexamine the function of the pattern. As a result, it has been confirmedthat the pattern was free from any short-circuited connection part,thereby demonstrating the favorable patterning of the counter electrodeof the organic EL element according to the present invention. It hasbeen confirmed that the organic EI element, even when preserved in theair at 20° C. and 60% RH for 5000 hours, was free from a defect in lightemitting element of 50 μm or larger in diameter, and was excellent insealing propeties.

Moreover, the non-light-emission state for the edges of the stripe lineswas examined at the same time. As the result, it has been confirmed thatthe non-light-emission width thereof was 3 μm or smaller, and also thatthe edges were favorably defined.

Further the sealing plate was pressed with fingers to check anyshort-circuits of the element. As the result, the element was entirelyfree from any short-circuits, since the inter-insulator layer was in theform of a column.

COMPARATIVE EXAMPLE 1

A photosensitive polyimide coating material (produced by TorayIndustries Inc. under the trade name “UR 3140”) was applied by spincoating onto a glass substrate holding an ITO as the lower electrodewhich had been subjected to striped processing, said glass substratebeing the same as that used in Example 1. The spin coating was carriedout at a number of revolutions of 4000 rpm for a revolution time of 30seconds. Subsequently, the coated substrate was dried at 80° C. for 30mimutes, and then was exposed to light through a photomask at anirradiation power of 80 mJ/cm².

By the subsequent development, a pattern of the polymer of a polyamicacid was obtained. The resultant pattern was cured at 180° C. for 30minutes in an oven in an N₂ atmosphere, and further cured at 300° C. for30 minutes, thus enabling to prepare an ITO/glass substrate with apolyimide layer as an inter-insulator layer. Thereafter the resultantITO/glass substrate was tesed in the same manner as in Example 2. As aresult, the value: {(width of the lower section)−(width of the uppersection)}/(height) was about 1. Then in the same manner as in Example 3,an organic EL element was prepared, and one line of ITO and one line ofMg:Ag were selected out of the stripe lines. A voltage was appliedthereto using ITO as the anode and Mg:Ag as the cathode. As a result, ithas been confirmed that there existed light-emitting portions inaddition to the intersecting part of the stripes of the ITO and theMg:Ag, and that the striped pattern processing of the Mg:Ag as thecounter electrode was unsuccessful under the foregoing conditions. Thespecimen after sealing was allowed to stand in the atmosphere at 20° C.and 60% RH. As the result, the light-emitting surface was markedlydecreased. This fact is due to that because of the highmoisture-absorption (usually 1 to 2%) of the polyimide as theinter-insulator layer, the inter-insulator layer absorbs moisture, andafter sealing, the moisture which has been absorbed in the polyimide isreleased therefrom, thus oxidizing the Mg:Ag as the counter electrode.

EXAMPLE 4 In the Case of the Inter-Insulator Layer Being aFluorine-Based Polymer

A solution of a fluorine-based resin (produced by Asahi Glass Co.,Ltd.under the trade name “Sitop CTX-809”) capable of forming aninter-insulator layer made of a fluorine-based resin having acoefficient of water absorption of at most 0.01% (in accordance withASTM D570) was applied by spin coating onto a glass substrate same asthat used in Example 1. The spin coating was carried out at a number ofrevolutions of 600 rpm for a revolution time of 30 seconds to form aSitop film with a film thickness of 4.8 μm. Then, the coated substratewas dried on a hot plate at 50° C. for 1 mimute, at 80° C. for 1 mimute,and at 120° C. for 1 mimute. As the final curing it was further dried inan oven at 250° C. for 1 hour.

Subsequently, a positive type photoresist (produced by Tokyo Ohka KogyoCo.,Ltd. under the trade name “TOPR-1000”) was applied to the film byspin coating at a number of revolutions of 3000 rpm for a revolutiontime of 20 seconds. Then, the coated substrate was dried on a hot plateat 110° C. for 90 seconds, and then was exposed to light with gamma rayat an irradiation power of 500 mw/cm² for 1 second, followed bydevelopment.

Subsequently, etching was carried out for 50 minutes by means of aplasma etcher as a dry etching apparatus, using a mixed gas containingCF₄, CHF₃, and Ar at flow rates of 24, 24, and 98 SCCm, respectively ata plasma output of 300 W under a vacuum degree of 0.5 Torr.

Then the cross section of the specimen was observed in the same manneras in Example 2. As a result, the value: {(width of the lowersection)−(width of the upper section)}/(height) was {fraction (1/10)}.

EXAMPLE 5 Preparation of Inter-Insulator Layer of Inversely Tapered Type

ZCOAT-1410(photosensitive polyolefin-based nagative type resist,produced by Nippon Zeon Co.,Ltd.) was made into a film by spin coatingon a glass substrate 2 with a thickness of 0.5 mm holding an ITO as thelower electrode which had been subjected to striped processing at apitch of 300 μm. The spin coating was carried out at a number ofrevolutions of 1000 rpm for a revolution time of 40 seconds. The filmthus obtained had a thickness of 8.8 μm.

Subsequently, the film-coated substrate was baked in a hot oven at 80°C. for 15 mimutes, and then was exposed to light through a photomask atan irradiation power of 450 mJ/cm² with ultraviolet ray with awavelength of 365 nm. The exposure pattern was carried out so that aninter-insulator layer having a width of 50 μm remains at a pitch of 350μm as linear lines perpendicularly to the pattern of the aforesasid ITOpattern. After development, curing was put into practice at 200° C. for1 hour in a clean oven to prepare an inter-insulator layer.

Then the cross section of the specimen was observed by means of ascanning electron microscope in the same manner as in Example 2. As aresult, the value: {(width of the lower section)−(width of the uppersection)}/(height) was negative, and the cross section was in aninversely tapered form as shown in FIG. 10 (b) or (c) throughout all ofthe observed cross sections.

EXAMPLE 6 Preparation of Organic EL Element and Evaluation of Precisionand Minuteness Thereof

By the use of the specimen which had been prepared in Example 5, anorganic EL element was prepared in the same manner as in Example 3. Thepattern precision was evaluated in the same manner as in Example 3. Asthe result, the pattern precision was ±4 μm, and it was confirmed thatthe pattern was free from any short-circuited connection part in thestripe lines of Mg:Ag, thereby demonstrating the favorable patterningmethod.

EXAMPLE 7 Preparation of Organic EL Element and Evaluation of Precisionand Minuteness Thereof

SiO₂ was made into a film with a thickness of 1 μm by a plasma-enhancedCVD method on a glass substrate 2 with a thickness of 0.5 mm holding anITO as the lower electrode which had been subjected to stripedprocessing at a pitch of 300 μm . The film formation conditions were setto a substrate temperature of 250° C., a vacuum degree of 0.7 Torr, anda plasma output of 200 W, using a mixed gas of N₂O and SiH₄ (1:1) as theplasma gas species.

Thereafter in the same manner as in Example 4, a positive typephotoresist (produced by Tokyo Ohka Kogyo Co., Ltd. under the trade name“TOPR-1000”) was made into a film, followed by exposure to light anddevelopment so as to leave a pattern in which opening lines are providedperpendicularly to the ITO that had been subjected to striped processingas mentioned hereinbefore. The opening lines had a width of 280 μm and apitch of 300 μm.

Subsequently, the SiO₂ at the opening portion of the photoresist wascompletely removed by plasma etching so that the surface of the ITO wasexposed. The SiO₂ etching was carried out, using a mixed gas of CF₄,CHF₃, and Ar (ratio by volume of 1:1:3.5) as the plasma gas species at avacuum degree of 0.5 Torr, and a plasma output of 300 W. The SiO₂ thatwas used as the inter-insulator layer had an extremely low coefficientof water absorption as low as 0.01% or lower.

Thereafter an organic EL element was prepared in the same manner as inExample 3, and was evaluated. As the result, there were obtainedfavorable pattern precision of only 1 μm or less, and also favorablepatterning of the counter electrode.

EXAMPLE 8 Preparation of Organic EL Element and Evaluation of Precisionand Minuteness Thereof

SiO_(x)(x=1.8) was made into a film with a thickness of 300 nm bysputtering method on a glass substrate 2 with a thickness of 0.5 mmholding an ITO as the lower electrode which had been subjected tostriped processing at a pitch of 300 μm.

Thereafter in the same manner as in Example 4, a positive typephotoresist (produced by Tokyo Ohka Kogyo Co.,Ltd. under the trade name“TOPR-1000”) was made into a film, followed by exposure to light anddevelopment so as to leave a pattern in which opening lines are providedperpendicularly to the ITO that had been subjected to striped processingas mentioned hereinbefore. The opening lines had a width of 280 μm and apitch of 350 μm.

Then the photoresist along with the substrate was heated to 150° C. sothat the cross section of the photoresist was made into asemicylindrical shape.

Subsequently, etching was carried out with a plasma etcher under theetching conditions including a mixed gas of CF₄, CHF₃, and Ar (ratio byvolume of 1:1:8) as the plasma gas species, a vacuum degree of 0.2 Torr,and a plasma output of 200 W.

Thereafter the photoresist was peeled off, and a first inter-insulatorlayer was prepared. The aforesaid photoresist having a cross section ina semicylindrical shape was intended to render the cross section of thefirst inter-insulator layer trapezoidal. Further the SiO_(x) wasprocessed into a trapezoidal shape through a plasma etching method.

After the aforesaid step, ZCOAT-1410 was made into a film on theabove-mentioned first inter-insulator layer in the same manner as inExample 5 to prepare a second inter-insulator layer. Both the firstinter-insulator layer and the second inter-insulator layer had anextremely low coefficient of water absorption as low as 0.01% or lower.

Thereafter an organic EL element was prepared in the same manner as inExample 3, and was evaluated. As a result, there were obtained favorablepattern precision of only 1 μm or less, and also favorable patterning ofthe counter electrode.

INDUSTRIAL APPLICABILITY

The organic EL element according to the present invention is anexcellent organic electroluminescent element which is highly precise andminute, uniform in light emission, free from cross talk, resistant toexternal pressure, and further excellent in sealing properties.

Thus, the organic EL element according to the present invention is wellsuited to use for a display which is highly precise and minute, anduniform in light emission such as OA equipment and machinery, clocks andwatches.

What is claimed is:
 1. An organic electroluminescent element 1 that is equipped, between a lower electrode 3 and a counter electrode 4 each on a substrate 2, with: an intervening organic layer 5 comprising a light-emitting layer, which element 1 comprises an inter-insulator layer 6 having a coefficient of water adsorption of at most 0.1% in a non-light-emitting element portion; step portions 9 in said inter-insulator layer 6, said step portion 9 defining the boundary between a light-emitting element portion and a non-light-emitting element portion and containing rising parts almost perpendicular to the surface of said lower electrode 3; and a sealing plate or a sealing lid 7 which is placed over said inter-insulator layer 6 which is attached to said substrate 2 via an adhesive layer
 8. 2. The organic electroluminescent element 1 according to claim 1, wherein a space encompassed by the sealing plate 7 and the substrate 2 is filled in with a fluorinated hydrocarbon as a sealing liquid.
 3. The organic electroluminescent element 1 according to claim 1, wherein a space encompassed by the sealing plate 7 and the substrate 2 comprises a moisture absorbing agent.
 4. The organic electroluminescent element 1 according to claim 1, wherein a moisture absorbing layer is placed on the inner side of the sealing plate 7 and/or the outer side which is in contact with the outside of the organic EL element.
 5. The organic electroluminescent element 1 according to claim 1, wherein a space encompassed by the sealing plate 7 and the substrate 2 comprises a sealing gas selected from the group of dehydrated nitrogen, carbon dioxide and helium.
 6. The organic electroluminescent element 1 according to claim 1, comprising a color filter placed on a sealing plate
 7. 7. The organic electroluminescent element 1 according to claim 1, comprising a color filter placed in the sealing plate 7 and above the counter electrode
 4. 8. The organic electroluminescent element 1 according to claim 1, comprising a color conversion film placed on the sealing plate
 7. 9. The organic electroluminescent element 1 according to claim 1, comprising a color conversion film placed in the sealing plate 7 and above the counter electrode
 4. 10. The organic electroluminescent element 1 according to claim 1, wherein the organic electroluminescent element 1 is addressed by an active matrix.
 11. An organic electroluminescent element 1 that is equipped, between a lower electrode 3 and a counter electrode 4 each on a substrate 2, with: an intervening organic layer 5 comprising a light-emitting layer, which element 1 comprises an inter-insulator layer 6 having a coefficient of water absorption of at most 0.1% in a non-light-emitting element portion; step portions 9 in said inter-insulator layer 6, said step portions 9 containing portions rising in the form of an inverse taper almost perpendicularly to the surface of the lower electrode 3 and dividing said counter electrode 4 into a plurality of individuals; and a sealing plate or a sealing lid 7 which is placed over said inter-insulator layer 6 and which is attached to said substrate 2 via an adhesive layer
 8. 12. The organic electroluminescent element 1 according to claim 11, wherein a space encompassed by the sealing plate 7 and the substrate 2 is filled in with a fluorinated hydrocarbon as a sealing liquid.
 13. The organic electroluminescent element 1 according to claim 11, wherein a space encompassed by the sealing plate 7 and the substrate 2 comprises a moisture absorbing agent.
 14. The organic electroluminescent element 1 according to claim 11, wherein a moisture absorbing layer is placed on the inner side of the sealing plate 7 and/or the outer side which is in contact with the outside of the organic EL element.
 15. The organic electroluminescent element 1 according to claim 11, wherein a space encompassed by the sealing plate 7 and the substrate 2 comprises a sealing gas selected from the group of dehydrated nitrogen, carbon dioxide and helium.
 16. The organic electroluminescent element 1 according to claim 11, comprising a color filter placed on a sealing plate
 7. 17. The organic electroluminescent element 1 according to claim 11, comprising a color filter placed in the sealing plate 7 and above the counter electrode
 4. 18. The organic electroluminescent element 1 according to claim 11, comprising a color conversion film placed on the sealing plate
 7. 19. The organic electroluminescent element 1 according to claim 11, comprising a color conversion film placed in the sealing plate 7 and above the counter electrode
 4. 20. The organic electroluminescent element 1 according to claim 11, wherein the organic electroluminescent element 1 is addressed by an active matrix.
 21. An organic electroluminescent element 1 that is equipped, between a lower electrode 3 and a counter electrode 4 each on a substrate 2, with: an intervening organic layer 5 comprising a light-emitting layer, which element 1 comprises a first inter-insulator layer having a trapezoidal cross section 15 on said lower electrode 3 as a non-light-emitting element portion; a second inter-insulator layer 14 above said trapezoidal cross section; step portions 9 in said second inter-insulator layer 14, said step portions 9 containing rising parts almost perpendicular to the surface of the lower electrode 3 and dividing said counter electrode 4 into a plurality of individuals; and a sealing plate or a sealing lid 7 which is placed over said second inter-insulator layer 14 and which is attached to said substrate 2 via an adhesive layer
 8. 22. The organic electroluminescent element 1 according to claim 21, wherein a space encompassed by the sealing plate 7 and the substrate 2 is filled in with a fluorinated hydrocarbon as a sealing liquid.
 23. The organic electroluminescent element 1 according to claim 21, wherein a space encompassed by the sealing plate 7 and the substrate 2 comprises a moisture absorbing agent.
 24. The organic electroluminescent element 1 according to claim 21, wherein a moisture absorbing layer is placed on the inner side of the sealing plate 7 and/or the outer side which is in contact with the outside of the organic EL element.
 25. The organic electroluminescent element 1 according to claim 21, wherein a space encompassed by the sealing plate 7 and the substrate 2 comprises a sealing gas selected from the group of dehydrated nitrogen, carbon dioxide and helium.
 26. The organic electroluminescent element 1 according to claim 21, comprising a color filter placed on a sealing plate
 7. 27. The organic electroluminescent element 1 according to claim 21, comprising a color filter placed in the sealing plate 7 and above the counter electrode
 4. 28. The organic electroluminescent element 1 according to claim 21, comprising a color conversion film placed on the sealing plate
 7. 29. The organic electroluminescent element 1 according to claim 21, comprising a color conversion film placed in the sealing plate 7 and above the counter electrode
 4. 30. The organic electroluminescent element 1 according to claim 21, wherein the organic electroluminescent element 1 is addressed by an active matrix.
 31. A process for producing an organic electroluminescent element 1, comprising at least one step of forming a lower electrode 3 on a substrate 2; a step of forming a patterned inter-insulator layer on said lower electrode 3, a step of forming an organic layer over said lower electrode 3, and at least one step of forming a counter electrode 4 in the form of film, so that a first inter-insulator layer 15 has a trapezoidal cross section, a second inter-insulator layer 14 is mounted above said trapezoidal cross section, step portions 9 in said second inter-insulator layer 14 contain rising parts almost perpendicular to the surface of said lower electrode 3, and said counter electrode 4 is subjected to patterning processing at said rising part. 